You could......catch the ferry to Water Island and hang at Honeymoon Beach. Stop in at Gourmet Gallery to pick up sandwich and drinks as I don't know if Heidi will be grilling/open on Christmas Day. There are bathrooms at Honeymoon Beach (no showers but there are sinks). You could wash off the important parts, put your wet suits in a ziploc bag, put on a change of clothes, and catch the 3:15 ferry to the airport. The WI ferry is about an 8 minute ride. Taxi from Crown Bay to the airport is about 5-8 minute ride. Make sure to pre-arrange for taxi to pick you up at Crown Bay around 3:25.

You might check to see if you can do a "day pass" kind of a thing at one of the Best Western hotels by the airport. Maybe STTResident or another STT local can help with phone numbers. I don't know whether they actually do that but some hotels have a "day room" where you can change and get ready to leave for the airport.

You won't need a day pass for either of them. It's a public beach and as long as you patronize the beach bars it won't be an issue. That would be my idea of a good way to spend the day prior to departure. Either Island Beachcomber or The Best Western Emerald Beach.
Jay

Thanks for the suggestions. I want to squeeze every moment possible out of the USVI! 🙂

Pay a little extra and keep the car.

Take a slow tour around STT North Shore and West End
Slow lunch
Then to the Island Beachcomber or The Best Western Emerald Beach for one last cool one
Walk on to the plane mellow and ready to travel

i would spend the last day at coral world. There is a lot to do there, and you can eat lunch there as well. My favorite thing to do was go to the beaches and spend the whole day relaxing. At some beaches the bar tenders come up to you and ask your order and will bring your drink right to you. 🙂